The recent brouhaha about the voluntary payment for plastic bags in a supermarket chain raises more general questions.

It is supposed to be an offence, punishable by a severe fine, to consume food or drink on an MTR train.

However, these days you will see people eating and drinking in every carriage - a situation which becomes more common as each month passes.

That 'prohibition' is ineffective, because no one enforces it.

Live-in foreign maids sign contracts with their employers for a certain minimum amount. However, there are thousands of cases where dishonest employers underpay and yet the Labour Department prosecuted only 32 cases in 2005, and a derisory 13 in 2006. The Indonesian and Philippines consulates need to be more proactive in seeking legal protection for their abused compatriots. Without enforcement action, the legal minimum wage for them will continue to be widely flouted.

It is pretty generally recognised that the voluntary minimum wage scheme is little more than window-dressing. Paying staff (who may have few other employment options) a pittance for long hours diminishes the quality of human life, and does not fit well with Hong Kong's great wealth. Decent employers will pay a fair wage without prompting, but those less generous need more than a voluntary scheme to make them cough up.

To discourage us from using so many plastic bags, which add to our already overburdened landfill sites, clearly a charge needs to be imposed by all supermarkets to all customers requesting a bag.

The other day, I observed a supermarket customer take five bags, to wrap up a few pieces of fruit.

Such wanton thoughtlessness will only be discouraged by the supermarket chains biting the bullet and charging for all the bags they distribute.

While it is all very well to rely on voluntary methods for some matters (such as how much annual bonus to pay employees), some more basic ones demand schemes which oblige adherence to fair standards.